Cognition during childhood is innately stronger and this declines with aging. To speak a language fluently, you would have been exposed to people speaking the language since your childhood. I still remembered one thing I did recited during my childhood up to this day bafter long period of time I did not recite it again. It was one when I was a child, I made it like 8 during my teen age, but I forgot the whole 7 completely while still remember the first I had known during my childhood.

There are long term memory and short term memory. There are numbers (although not long) I still remember because I have known it for long and put it to daily use, like my dad and mum phone numbers, I can never forget both. But there are still numbers that I thought I have learnt but I forgot because I did not put them into use. Not putting something into use will result into the information gradually fading away from someone's memory.

It is certain that seed phrase, seeds and many other things related to wallet including what is in the OP will not be in frequent used, this will finally and easily result to forgetfulness of it. That is why seed phrase or anything related can not be memorized which is perfectly wrong because the person can not turn it into morning, afternoon and night anthem for years, while not forgetting after not uising it as anthem again is not guaranteed, which can result to coin loss.

The only outside of BIPs which is better but which I can not recommend is Shamir secret sharing, which will convert seed phrase or anything to encrypt into characters which I do not prefer unlike the seed phrase itself which is easy to write down and backup, while passphrase can be included but backup in different location to increase the backup security, while also multisig is a good way to go about this.